Sintered dolomite is required for the manufacture of fire resistant shaped bodies. It is qualitatively the more valuable, the denser it is sintered, and the fewer contaminations it contains. If possible, sintered dolomite is sintered from lumpy raw dolomite in a so-called penetration-by-burning process in a shaft kiln or in a rotary kiln, wherein solid fuels, cinder or anthracite are admixed to the lumpy raw dolomite; the sintering in the rotary kiln, however, is accomplished mostly with a coal dust or oil firing, less frequently with natural gas. The rotary-kiln sintered dolomite is more uniform with respect to the shaft kiln sinter, as far as its quality is concerned. The shaft kiln sinter requires, at more than 97% carbonate content of the raw dolomite by weight, a heat expenditure of more than 8000 kJ/kg sinter; modern rotary kilns, however, require a heat amount of more than 7000 kJ/kg sinter for the manufacture of sintered dolomite, but admittedly need a high-grade, and therefore expensive fuel.
Furthermore, in exceptional cases, particularly when the raw dolomite is very non-uniform in its composition, or if it is hard to sinter, or if too low MgO contents are present, the sintered dolomite is manufactured in a so-called double penetration-by-burning process. In the first sintering, the raw dolomite is sintered merely caustically, then ground, possibly mixed with additional materials, formed to pellets or pressed into briquettes, which are then sintered in a shaft kiln or rotary kiln. The heat expenditure for this process differs according to the sintering aggregates used, but is very high, so that it is used only in exceptional cases.